I know this is a little old, but I just ran into a similar problem and someone pointed me in the right direction.
If your server is sending back a JSON encoded resonse, but you only pass it a single value (191 in your case), $resource seems to interpret it as a string, which it is then splitting into an array of individual characters (I'm not 100% on the technical details of why, but that was my experience). So what you need to do is send back your value wrapped inside of a JSON object.
So, instead of doing something like:
function callback(req, res) {
var number = 191; // this is just for example purposes
res.json(number);
}
You need to do something like:
function callback(req, res) {
var number = 191; // again, just for an example
res.json({ value: number });
}
Then when your $resource call comes back, just access the value
property of the response and you should be good to go.
P.S. The examples here are based on a Node/Express back end, not Spring, but I think this should still apply.